In typical imaging situations, an imaging system is designed for best performance and production of sufficient quality images for average expected lighting conditions. Images may be collected from a large variety of conditions and locales; indoor scenes with artificial lighting, such as incandescent or fluorescent lighting, may vary significantly from outdoor scenes under bright sunlight.
Composite lighting conditions, mixing indoor and outdoor lighting characteristics, are also possible. For example, the imaging system may be located inside of a building while imaging a scene that includes poorly illuminated dark-colored objects within the building as well as brightly sunlit light-colored objects outside of the building. Such a combined indoor and outdoor scene may require imaging of a set of objects that range in intensity over multiple orders of magnitude.
Intensity of a scene or an object may be formally characterized by measuring the luminance of specific objects within the scene. Luminance is defined as the number of candelas per square meter (“cd/m2”). For instance, a dark wooden surface may have a luminance of less than 1 cd/m2, a light colored wall may have a luminance of approximately 10 cd/m2, a concrete parking lot may have a luminance of approximately 1,000 cd/m2 and the sky may have a luminance of greater than 10,000 Cd/m2.